In processes in which gas suspended solids such as catalyst or coke are contacted or reacted in metal vessels at relatively high temperature conditions, it is conventional to line the interior of the vessel with a suitable refractory material to insulate the metal wall of the vessel from the process temperatures as well as to protect the metal wall from the corrosive and erosive effects of the material being processed within the vessel.
There are several conventional methods for installing insulating linings in such "cold wall" reactor vessels. One method is to secure a pre-cast or molded refractory brick lining to the vessel internal wall by metal anchors, adhesives or the like. Another method is to cast or gun a castable refractory lining in place inside the vessel.
None of these methods has proved entirely satisfactory for a number of reasons. Thermal stresses often result in cracking of the lining and its separation from the wall during thermal cycling of the reactor with the concomitant loss of heat from the vessel and access of the hot gases and erosive solids to the vessel wall. As a consequence, the lining requires repair which is costly in terms of material labor, and also in terms of loss of production from downtime of the reaction vessel.
Consequently, numerous attempts have been made to improve on the method of installing refractory linings in vessels requiring them. For example, in U.S. Pat. No. 2,398,546 there is disclosed a vessel lining system which consists of a refractory lining which is spaced from the vessel wall. A particulate refractory material is included within the space between the wall and the lining, serving to insulate and minimize contact of the wall by erosive solids.
In U.S. Pat. No. 2,982,623, a monolithic thermal insulating lining for a vessel is disclosed which includes a metal grid spaced from the vessel wall by studs. The metal grid has two castable layers applied to it. The first layer is a low density, high insulating castable refractory. A second layer contains an abrasion resistant castable. It is included to protect the refractory layer from erosion.
U.S. Pat. No. 4,490,333 discloses a dual insulating layer in a reactor vessel using a ceramic anchor to fasten the second refractory layer to a previously-applied first insulating layer. Dual layer systems as represented by the foregoing references, of course, frequently fail because of the thermal stresses between the two layers. Moreover, they tend to be expensive to install and repair. Special anchoring systems are sometimes necessary for satisfactory installation of these.
In U.S. Pat. No. 4,490,334 there is described the use of curved ribs and mesh to hold a ceramic fiber blanket in place in a domed portion of a cylindrical reactor. Use of a ceramic fiber blanket in this application is practical only because the fiber blanket is not exposed to erosive fluidized solids which would otherwise quickly destroy the blanket.
Since there has been a trend toward conducting petrochemical processes at ever more severe conditions than heretofore, further improvements in lining systems used in cold wall reactor vessels is even more important. Changing economic conditions and the necessity to increase productivity are additional factors driving the constant search for improved lining systems for reactor vessels.
Accordingly, it is an object of the present invention to provide an improved erosion-resistant ceramic insulating lining system for cold wall vessels which is heat resistant.
It is another object of the present invention to provide an improved erosion-resistant ceramic insulating lining for cold wall vessels that can be installed at lower cost than other lining systems.
These and other objects of the present invention will be apparent from a reading of the description which follows.